1. Field of the Invention
The present invention relates to a solid-state image sensor and an image-capturing device equipped with the solid-state image sensor.
2. Description of Related Art
Today, video cameras and electronic cameras often come equipped with an AF (autofocus) function as a standard feature. Such a camera normally includes a solid-state image sensor constituted with a CCD or a CMOS. The solid-state image sensor includes a plurality of pixels equipped with photoelectric conversion units that generate signal charges in correspondence to the amount of incoming light, disposed in a two-dimensional array. On-chip micro-lenses are disposed on the light-entry side of the photoelectric conversion units. The micro-lenses are disposed in order to condense light that would otherwise enter pixel areas Other than the photoelectric conversion units onto the photoelectric conversion units and thus increase the amount of light entering the photoelectric conversion units.
A single lens reflex electronic camera often includes a focus detector adopting the split-pupil phase difference method, provided as a separate unit in addition to the solid-state image sensor engaged in the image-capturing operation so as to detect the focusing state quickly. However, during the focus detection, no subject light enters the image sensor and, for this reason, no live view image display is provided on the compact monitor installed at the rear side of the camera. While the live view image is displayed, on the other hand, no subject light enters a focus detector that detects the focusing state through the split-pupil phase difference method. This means that focus detection cannot be executed via the focus detector during live view image display. While technologies whereby focus detection is executed through the contrast detection method (peak method) based upon signals provided from the solid-state image sensor have been proposed, focus detection cannot be executed quickly through such a method. To address this issue, Japanese Laid Open Patent Publication No. 2003-244712 and Japanese Laid Open Patent Publication No. 2006-261292 each disclose a solid-state image sensor that includes built-in focus detection pixels to be used in focus detection through the split-pupil phase difference method.